The present invention relates to a new and improved construction of a gas-blast switch.
Generally speaking, the gas-blast switch of the present development is of the type comprising a stationary contact element and a movable contact element which can be brought into and out of engagement with one another within a switching chamber. The switching chamber flow communicates, on the one hand, by means of a blast nozzle, which is closed in the cut-on position of the gas-blast switch by the movable contact element, with an expansion chamber and, on the other hand, flow communicates by means of the non-return or check valve which is open towards the switching chamber with the pressure side of a stationary pump cylinder arranged within the expansion chamber. Operatively associated with this pump cylinder is a movable pump piston which, during a cut-off stroke of the gas blast switch pressurizes the pump cylinder with a time-delay.
Such type gas-blast switch is known, for instance, from FIG. 2 of German Patent Publication No. 2,750,762. With this prior art gas-blast switch the desired time delay of the actual pumping stroke of the pump piston is realized in that, the movable contact element and its switching rod, respectively, are coupled by a spring-loaded drag connection with the pump piston. Hence, during a cut-off stroke the pump piston initially then begins to carry out its pumping stroke when the movable contact element and its switching rod have moved through a part of the cut-off stroke which is determined by the nature of the drag connection. The time-delay of the pumping stroke is desired because there is not required pressurized extinguishing gas for blowing of the formed switching art immediately at the start of the cut-off stroke, so that the power output which must be applied by the switch drive for performing the pumping stroke initially is completely available for accelerating the movable components of the switch out of the cut-on position.
Therefore, with the state-of-the-art switch the pump piston is movable to a limited degree in relation to the movable contact element and its switching rod, and furthermore, the drive, at the start of the cut-off stroke, must overcome the force of a spring provided at the drag connection. If, however, for some reason, whether such be because of faulty lubrication or because of binding due to deposition of abraded particles, the mobility of the pump piston in relation to the movable contact element is no longer completely insured for, i.e. if the drag connection no longer functions or only hesitatingly functions, then with the heretofore known gas-blast switch the pump or pumping stroke begins at the start of the cut-off stroke, in other words too early, so that the power output of the switch drive possibly is no longer adequate.